Re: Orionids, Taurids and Leonids... Oh My!
t_wade wrote:
Very nice! I love capturing meteors. The bottom two may actually be flaring satellites. Sometimes it is very hard to tell the difference.
You're right, it is hard to tell the difference and when I was showing my time lapses after Thanksgiving dinner last night one viewer commented "oh the shooting stars!". I explained that what she was seeing were airplanes and satellites because it is virtually impossible to spot meteors in the time lapses when they are just 1 of 24 frames per second (unless there's an ion train which is one reason why they are exciting).
I've seen a time lapse recently where the video was slowed down to emphasize a meteor that was just a single still that they faded in and out in order to really emphasize it. I suppose I could do something like that too for the people who want to see meteors in my time lapses, but it is a lot more work than my current compilation process.
So knowing the likelihood for confusion I do a careful frame by frame analysis of my stills and use these criteria to help me determine what I'm looking at.
1) The satellites and airplanes typically appear in 3-4 frames depending on the direction they're traveling relative to my camera. Anything that only appears in a single frame is usually a meteor, unless it is close to sunrise. I've observed that as the sun is just rising I can often see numerous satellites in every frame and they are often flaring and only appearing in 1-2 frames.
2) The meteors almost always have tapered trails where the planes and satellites are blockier on the ends, unless it is close to dawn. The meteors often have more green in their trails too, but neither of these is a sufficient diagnostic by itself and I generally can't tell from just one single photo what I'm looking at.
3) Persistent ion trains provide a dead giveaway of meteors, as with the one entitled "Leonid at the Crack of Dawn". The bulge in the middle of that meteor is the ion train beginning to deform. It was visible in several subsequent frames until sunrise washed it out. The only danger in using an ion train is an airplane contrail false positive, but criteria #1 almost always applies to airplanes in a clear sky (I'm having an email discussion about contrails with a relative who believes in chemtrails, and have been educating myself over the years about contrails with help from a friend who is an atmospheric physicist and who has consulted with a major manufacturer on the problem of contrail cirrus over Europe).
This process got me thinking a bit recently... I have stills with multiple planes and satellites in the sky, sometimes crossing each other's trails. Those photographs look at lot more impressive when you don't know what you're looking at. So what makes the genuine meteor photos so special then? They're just little streaks of light and not all that visually impressive. It is more what they are than how they look, which is why I try to be very careful with my identifications.
Mike